Medical optometry should be tailored to the wearer’s actual situation, and the choice of medical optometry is a prerequisite for accurate prescription, only professional medical optometry can be scientific, healthy and comfortable correction and control of myopia. In medical optometry, dilated pupils are a very important step. 1. Who needs dilated lenses? (1) Children under 15 years of age must have their pupils dilated because their eyes are highly regulated, and the younger they are, the stronger the regulation. A strong pupil dilator, atropine, is generally used. (2) For myopia between the ages of 16-30 and hyperopia between the ages of 16-40, the pupils need to be dilated for the first eye exam, but you can use a medium-acting dilating agent – posterior atropine. For the second and subsequent prescriptions, the pupils may or may not be dilated depending on the situation. (3) For more complex refractive errors, such as higher degrees of myopic astigmatism, mixed astigmatism high myopia, high astigmatism, etc., the pupil dilatation is more accurate, such as no pupil dilatation error is larger. (4) Some diagnostic optometry, fundus and refractive quality are normal, but poor vision, need to use optometry to exclude the presence of refractive error, need to dilate the pupil optometry. (5) For small pupils after optometry, poor vision correction or refractive interstitial clouding, dilated pupil optometry should be performed. (6) Youth with reduced vision or unstable vision (vision can be good or bad at any time), should be dilated for optometry. 2. The following people should not or need not have their pupils dilated: (1) Those with a diagnosis or suspicion of primary angle-closure glaucoma, or those whose examination reveals a shallow anterior chamber and high intraocular pressure, should not have their pupils dilated. This is because dilating the pupil can induce an attack of closed-angle glaucoma with elevated intraocular pressure and more serious consequences. Pupil dilators must be used under the direction of a physician. (2) Over 40 years of age, the adjustment power is already weak, and generally has less effect on the optometry, so you can not dilate the pupil. (3) Severe refractive interstitial clouding, such as cataracts and severe vitreous opacities, make optometry impossible and make pupil dilatation unnecessary. (4) Those with severe pupillary adhesions that cannot be dilated.